Apparatus for plasticizing and straining plastic material



Nov. 22, 1949 HENNING 2,488,595

4 APPARATUS FOR PLASTICIZING AND STRAINING PLASTIC MATERIAL Filed Aug. 50, 1946 2 sheets*sheet 1 lNl/ENTOR GE. HE NN/NG AT-TORNEY Nov. 22, 1949 G. E. HENNING APPARATUS FOR PLASTICIZING AND STRAINING PLASTIC MATERIAL 2 Sheets-Sheet 2 Filed Aug. 30, 1946 he. a

//v VEN TOR GE. HENN/NG ATTORNEY isshotvn in Fig. 1 an extruder, which is designed Patented Nov. 22, 1949 P1 2,488,595

UNITED (s TATES mama Aii PIARAKruSQFQR msineizinte STRAINING PLASTIC MATERIAL George 5. pantie-gynae- 'reg fiaz; as; Western Electrio eomp Iii'odrboi'atfl; York, N. Y, aiirporatifi (if-New York intimation 'Aug'iit' 'so, miaseeri 'l-blaifii's. (ch l s-21 i) 1 l This invention relates to apparatus "for isms: tieiirig'anfl'lstraining plastic material. In the inanufacture'bfpreduets from 'blastic a1 seen as a vulcaniiabl'e compoundineluding riibb'r' or a synthetic rubbr-likeinaterial, it is often a'dtiantageb'us to plastieiz'e'the material and to strain the material While in the ex en e In the past, no strainers have been e known feistraining from'the material elongated, f5 having "a tap needle-like particles, which knight produce faults ee'ntiiiuationbf" iftherhatefialis'used'jor electrical insulation. 7 Qhjeet df the invention is to provide new aim iii iprbii'd apparatus for plasticizing and straining plasma; material.

"ap ratus illustrative of the invention inelud'esla onduit and rriean'sfor forcing plastic matenarjtnrqugh the conduit. pair of breaker plates any; assages extending thereth'rough arepjositiohed nearthe exit -lend of the conduit, With'the passages in one of the plates staggered with respect to the 'passages'in the other plate, apda fiust d bofiical straiheris pdsitibned in the exit of the conduit. The strainer includes "a frustd-fgd" dal b'ae'king plate having relieved pasdie hplder sagestherein, a backing sereenjmounted on the 25 h m n haeki'rig plate, and a 'st'rainin'g sereen positioned on the hacking Screen. Thernateria1 is forced through the extrusion passage in one direction, and 'ismr'aeu through the strainer in directions ant'ially perpendicular to the first inention'ed direction its a result, elongated needle like faultra iating particles are l pressed laterally st the s rainer and are'strair'ied thereby. v Iaror other'shape'd particle's likewise "are mqvedb y 1 fs eihr. fh prnplet understanding r the invention may Hetbtaineu from the following detailed descriptidnbf "an apparatus forming aspecifie'embodig ooves f nent thereof, when read in conjunction Withtlie gfiobiiries appen e drawings, inwhich: W I 4b 'Fi'g 1is a fragmentary, ho'rizbntal sectin of aq appamtus forming" 'one embodiment of the invenfio'n; H I p Fig. 2 is an enlarged, fragmentary, vertial 's' e"tion taken'along'line 2 2 of' Fig. 1, and 1' 5 4 Fig.3 is an enlarged perspective view of'aportign of the apparatus 7 e I Referring new in detail to the drawings there tojapply a overing of plastieimateriaLsuChas a, '55 uuleanizable compound fi'ncluding rubber or "a synthetic rubberlike material, on "afila'rnentaiy t')nductor 9, tvh i ch fmay be barefor coveredwitha te I "c "'ooverin gn The "xtruder jin- Fig 1 eludes an"ektrus1b of the screens 43 and 50 and the backing plate 40, which fit closely therein. The boss 31 of the support 38 has an annular socket 56 for receiving the lower ends of the screens 43 and 50 in closefitting engagement.

A second breaker plate so having a plurality of radiallyextending slots (SI-6| is oriented with respect to the breaker plate 5| by dowels, of which a .dowel B2 is shown. The dowels 62-62 fit into bores, of which a bore 63 is shown, formed in the breaker plate 60, and bores, of which a bore 64 is shown, formed in the breaker plate 5|. The breaker plate 60 is held by the dowels 62-62 in a position in which the slots GI-Bl therein are staggered with respect to the slots 52-52 formed in the breaker plate 5|, so that streams of plastic material flowing through the slots SI-BI divide to flow through the slots 52-52, whereby the material is plasticized as it flows past the two breaker plates, which in efiect are staggered combs.

In the operation of the extruder described hereinabove, the elongated stock screw I2 is rotated and forces the plastic material through the extrusion bore ll formed in the extrusion cylinder H1 in the direction of the arrows in Fig. 1. The stock screw works the material as it advances the material through the extrusion bore, which working plasticizes the material somewhat. The material is forced from the stock screw to the breaker plate 50 in directions generally parallel to the axis of the extrusion bore H with any needle-like fault-producing particles therein travelling substantially endwise therewith as they are carried by the material. The material flows through the slots til-5| in the breaker plate 60, and then flows through the slots 52-52 in the breaker plate 5|. Since the slots 52-52 are staggered with respect to the slots til-6| and the slots 5l-5l and Bl-Bl are small in cross-section relative to that of the extrusion bore H, the material must flow through narrow tortuous paths in flowing past the breaker plates 5| and 60 and is thoroughly plasticized in so doing.

After the plastic material is forced through the slots 52-52 in the breaker plate 5|, it flows seriatim through the straining screen 50, .the backing screen 43 and the passages 4 l-4I in the backing plate 40. The directions of flow of the material change sharply as the material approaches the straining screen 50 and then are substantially radial with respect to the strainer so that the needle-like particles in the material are moved substantially laterally to the strainer. The screen 50 catches the needle-like particles when they are moved laterally thereagainst, which it might not always do so if the needle-like particles were moved endwise to it.

Hence, the straining. screen 50 strains out all oversized particles, including needle-like particles, in the material being forced therethrough and the backing screen 43 supports the fine straining screen 50. The backing plate 40 serves to support the heavy backing screen 43, and the annular grooves 42-42, which are in communication with the passages 4 [-4 I, provide channels of flow to the passages 4l-4l, whereby the effective straining area of the screen is largerthan it would be if the grooves 42-42 were not provided. As a result, the extruder may be operated for long periods of time without cleaning the straining screen 50 thereof. v

-Also, the frusto-conical shape of the straining screens 43 and 50 and the backing plate 40 provide a very large effective straining area of the screen 50. Hence, relatively large proportions of the straining screen 50 may be clog ed by oversized particles strained from the plastic material, and still leave sufilcient unclogged areas of the straining screen 50 to permit ample material to flow through the straining screen. In addition, the straining surface is substantially parallel to the main directions of flow of the material in the extrusion bore H. The material, after it has passed through the working and straining device 39, is directed -by the guide 54 toward the tapered opening I6 and flows through the die 23, which forms the material into a covering over the conductor 9, which is advanced continuously toward the right, as viewed in Fig. l.

The working and straining device 39 serves to effectively plasticize and strain the material being extruded without plasticizing and straining operations prior to the insertion of the material into the extruder. The device 39 is compact but is very effective and permits ample flow of the material for long operating runs without stopping the extruder to clean or replace the straining screen 50. Furthermore, the device separates slim, elongated particles from the material as well as globular oversized particles.

What is claimed is:

1. An apparatus for plasticizing and straining plastic material, which comprises a conduit, a stock screw rotatably mounted in the conduit for forcing plastic material through the conduit, a breaker plate positioned transversely in the conduit and having a plurality of passages therein, a second breaker plate positioned transversely in the conduit and having a plurality of passages, means for mounting the breaker plates in positions in which the passages in one of the breaker plates are offset with respect to the passages in the other and for spacing the breaker plates, a frusto-conical backing plate having a plurality of passages therein and fitting against one of the breaker plates, said backing plate being mounted transversely in the conduit, said backing plate being relieved adjacent to the passages therein for expediting flow of material therethrough, and a frusto-conical screen supported by the backing plate for straining oversized particles from the plastic material.

2. In a continuous extrusion apparatus including an extrusion cylinder having an extrusion bore therein, an extrusion head and means for forcing plastic material through the extrusion bore to the extrusion head, a working and straining device positioned between the extrusion cylinder and the extruding head comprising a plurality of combs for directing the plastic material in the exit end of the extrusion bore in small streams along tortuous paths to work the plastic material, and a frusto-conical strainer positioned between the combs and the extrusion head in axial alignment with the extrusion bore in the cylinder for straining oversized particles from the plastic material as the material is forced toward the extruding head.

3. In a continuous extrusion apparatus including an extrusion cylinder having an extrusion bore therein, an extruding head having a passage in communication with the exit end of the extrusion bore and means for forcing plastic material through the extrusion bore into the extrusion passage in the extruding head to cover a conductor being advanced through the extruding head, a working and straining device for separating the extrusion bore in the extrusion cylinder from the extrusion passage in the extruding head comprising a pair of breaker plates having a plurality of radially extending slots formed therein, means for mounting the breaker plates in positions relative to each other in which the slots in one of the plates are staggered with respect to the slots in the other plate, one of the said breaker plates being provided with a socket and having a tapered guide, a frusto-conical shell having an end designed to fit into said socket and to receive said guide, said shell being provided with a plurality of passages therein formed in annular rows and also being provided with a plurality of annular grooves formed in the outer portion thereof over the annular rows of passages, and a frusto-conical screen positioned over the frusto-conical shell for straining oversized particles from plastic material being forced from the extruding bore to the extrusion passage.

4. In a continuous extrusion apparatus including an extrusion cylinder having an extrusion bore therein provided with an exit end, said extrusion cylinder having a counterbore at the exit end of the extrusion bore, an extruding head having a passage in communication with the exit end of the extrusion bore and means for forcing plastic material through the extrusion bore into the extrusion passage in the extruding head to cover a conductor being advanced through the extruding head, a working and straining device for separating the extrusion bore in the extrusion cylinder from the extrusion passage in the extruding head comprising a pair of breaker plates having a plurality of radially extending slots formed therein, means for mounting the breaker plates in positions relative to each other in which the slots in one of the plates are staggered with respect to the slots in the other plate, one of the said breaker plates being provided with a socket and a tapered guide, a support provided with a frusto-conical shell and a boss for fitting into the counterbore in the extrusion cylinder, said shell having an end designed to fit into said socket, and serving to receive the guide, said shell also being provided with a plurality of passages therein formed in annular rows and having a plurality of annular grooves formed in the outer portion thereof over the annular rows of passages, and a frusto-conical screen positioned over the frustoconical shell for straining oversized particles from plastic material being forced from the extruding bore to the extrusion passage.

GEORGE E. I-ENNING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,595,470 J'ohnson Aug. 10, 1926 1,912,374 Johnson June 6, 1933 2,242,364 Montanau May 20, 1941 2,286,405 Gordon June 16, 1942 2,360,984 Schmitz Oct. 24, 1944 FOREIGN PATENTS Number Country Date 269,761 Great Britain Apr. 28, 1927 

